Christine Lagarde has warned that the escalating US-China trade war could deliver a "shock” to already struggling emerging markets, raising the prospect that a crisis ripping through Argentina and Turkey could spread across the developing world.

The IMF managing director told the Financial Times that her staff does not yet see "contagion” spreading to multiple countries beyond those currently fighting investor flight.

But she warned that "these things could change rapidly” and cited the "uncertainty [and] lack of confidence already produced by the threats against trade, even before it materialises,'' as one of the main dangers facing the developing world.

Lagarde’s comments came as Donald Trump, US president, is preparing to slap new tariffs on US$200 billion of Chinese imports, sharply ratcheting up the US trade war with Beijing. China vowed to retaliate and Trump has said he is prepared to impose levies on a further US$267 billion in Chinese products in response.

The brinkmanship has intensified just as emerging markets are struggling to win back market confidence after a sharp sell-off triggered by a rising US currency, which has raised questions about whether governments and companies can pay off billions in dollar-denominated debt.

So far, the developing world crisis has focused on Argentina and Turkey, both of which have specific fiscal or political issues that have raised investor concern.

But countries as diverse as South Africa, Indonesia and Brazil have in recent weeks seen outflows, raising the risk of a broader crisis, the FT reports.

Turkey’s central bank is due to meet tomorrow after signalling that it was prepared to raise rates to restore investor confidence, and Argentina has asked the IMF to speed up a US$50 billion bailout loan to shore up its finances.

Lagarde said the new austerity measures announced by Mauricio Macri, Argentina’s president, would be a "key determinant” of the fiscal policy going forward. The IMF, she said, was considering the Argentine request for a "rephasing” of payments.

Lagarde said that an increase in US-China tariffs would have a "measurable impact on growth in China” and would "trigger vulnerabilities” among its Asian neighbors because of their integrated supply chains.

She also said that the adverse impact in the US would mostly be felt by the "low-income people within the consumer population” who would be hit by higher prices on a wide range of goods.

"It would add a shock to a situation where there is no contagion but there are fragmented vulnerabilities. It would add an additional shock to it,” Ms Lagarde said of the developing world. "Trade is a positive, trade is a plus, trade needs fixing certainly but it is a tool and an engine for growth that should not be under threat, particularly at the moment.”